1 Corinthians 10:17

Believers, though many, yet are one body, and declare themselves to be one body mystical, by their fellowship together in the ordinance of the Lord's supper; as the bread they there eat is one bread, though it be made up of many grains of corn, which come into the composition of that loaf or piece of bread which is so broken, distributed, and eaten; and the wine they drink is one cup, one body of wine, though it be made up of many particular grapes. And they declare themselves to be one body, by their joint partaking of that one bread. Some have from hence fetched an argument to prove the unlawfulness of communicating with scandalous sinners at the Lord's table, because we declare ourselves one body with those that communicate: but whether it will (if examined) be cogent enough, I doubt; for one body signifieth no more than one church, and that not invisible, but visible. So as we only declare ourselves to be fellow members of the visible church with those with whom we partake in that ordinance, and the visible church may consist of persons that are bad mixed with the good. So as though, undoubtedly, scandalously wicked persons ought to be excluded from the holy table, yea, and no unbeliever hath a right to it; yet it may reasonably be doubted, whether those that partake with unbelievers, do by it own themselves to be unbelievers; they only own themselves members of that church wherein there are some unbelievers. But the scope of the apostle is from hence to argue, that by a parity of reason, those that communicated with an idolatrous assembly in their sacrifices, declared themselves by that action to be one body with those idolaters.